The present invention relates to a method for mapping internal body tissue, particularly body tissue inside or otherwise shielded by bone, and more particularly cranial soft tissue inside the skull.
The present inventor has recognized that at least brain soft tissue, and probably other soft tissue in the body, can exhibit changes to its structure during a short time-span, which can be as short as a few tens of milliseconds, in response to physiologic function and certain pathologies, such as a stroke or epileptic seizure. In addition, it is well known that the electric and magnetic fields produced by brain, heart or other tissue change rapidly over time in both normal and pathological function. Knowledge of these changes would therefore be useful to indicate the pathology and to monitor its progress or regress over time.
As is well known, the prior art has long used computer aided tomography (xe2x80x9cCTxe2x80x9d), which employs X-rays, to map interior body tissue. One readily appreciated problem with CT is that the X-rays do not provide good resolution of soft tissue. However, another major drawback of CT in the context of the aforementioned recognition is that exposure to X-rays is detrimental to health and therefore CT cannot be used for prolonged periods of time as a monitoring device.
Nuclear magnetic resonance imaging (xe2x80x9cMRIxe2x80x9d) is another well known method for mapping internal body tissue. MRI employs strong magnetic fields that are thought not to pose a significant health risk. MRI provides excellent resolution of soft tissue and is not hindered by bone surrounding the soft tissue. On the other hand, MRI has two major drawbacks. One well known drawback is that the machines are very costly and, therefore, machine time must be rationed. However, another drawback of MRI in the context of the aforementioned recognition is that the patient must be substantially completely immobilized during the time of imaging, which also prevents its use as a method for monitoring a patient over a prolonged period of time. The present inventor has also noted that MRI as it is currently provided is not adapted to seeing the changes in structure that are indicative of brain pathologies. There is a question whether this could be done given an appropriate motivation.
Accordingly, there is a need for a method for mapping internal body tissue that provides for the ability to discern structural changes in the body tissue that occur over very short times and to monitor such changes over prolonged periods of time, and to do so at particularly low cost making the method practical for widespread use.
The method for mapping internal body tissue of the present invention solves the aforementioned problems and meets the aforementioned needs by determining the spatial distribution of bone tissue of a patient that shields target soft tissue the structure of which it is desired to determine and monitor, and subjecting the patient to changing electric, magnetic or electromagnetic fields adapted for interacting with the target soft tissue as a function of the spatial distribution of the soft tissue. Electric, magnetic or electromagnetic energy that is transmitted through the bone and the soft tissue is analyzed to infer the spatial distribution of the soft tissue with the assistance of knowledge of the spatial distribution of the bone tissue.
Therefore, it is a principal object of the present invention to provide a novel and improved method for mapping internal body tissue.
It is another object of the present invention to provide a method for mapping internal body tissue that provides for the ability to discern structural changes in the body tissue that occur over very short times.
It is yet another object of the present invention to provide a method for mapping internal body tissue that provides for the ability to monitor such changes over prolonged periods of time.
It is still another object of the present invention to provide a method for mapping internal body tissue that provides for the ability to discern structural changes in the body tissue that occur over very short times and to monitor such changes over prolonged periods of time.
It is a further object of the present invention to provide a method for mapping internal body tissue that provides for any or all of the aforementioned objects at particularly low cost.
The foregoing and other objects, features and advantages of the present invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the following drawings.